Multiple studies have shown that zinc and a zinc-containing protein named ZAG are involved in lipid metabolism, satiety, and weight regulation, but zinc deficiencies are widespread, and having too much body fat can reduce blood levels of zinc, thereby increasing the risk of overweight and disturbances of the lipid metabolism. In a recent review article that is published in Nutrients, scientists look closer at zinc’s role in the lipid metabolism and why overweight people often lack zinc. The authors call for increased focus on zinc and end up concluding that it would be obvious to include zinc supplementation in the treatment of disrupted lipid metabolism and overweight.
Zinc is a trace element that is involved in over 300 enzyme processes and plays a role for growth and for macronutrient metabolism, which is the body’s turnover of carbohydrate, fat, and protein. Zinc is also involved in the regulation of inflammation, just like it is part of the SOD (superoxide dismutase) antioxidant. Animal studies and human studies have shown that lack of zinc may negatively affect growth, fertility, metabolism, immune defense, and numerous other processes. Overweight is a widespread lifestyle-associated disease that often requires treatment, which is why the authors of the new review article have analyzed 196 studies and articles from scientific databases to find out more about zinc’s role in macronutrient metabolism and weight loss.
Zinc, weight loss, and satiety
An analysis of the many studies shows that zinc improves the hepatic lipid metabolism and also has a positive impact on the lipid levels in the blood. Numerous studies have shown that zinc supplements given to overweight people significantly reduces blood levels of total cholesterol, LDL cholesterol, and triglycerides, potentially lowering the risk of cardiovascular disease and premature death. Some studies even indicate that zinc may raise levels of HDL, which is considered beneficial. Zinc is important for the synthesis of leptin, a substance that is related to metabolism, satiety, and the brain’s weight regulating center. More specifically, leptin belongs to a group of adipocytokines that are released by fat cells (adipocytes) in fat tissue. As mentioned, zinc is also an important antioxidant that can help prevent oxidative stress caused by free radicals. It appears that cholesterol, which is an essential compound, is not dangerous unless it is oxidized as a result of oxidative stress. This process causes the cholesterol to attach to the vessel walls where it sets the stage for atherosclerosis.
ZAG, lipid metabolism, and blood sugar levels
Zinc is of vital importance to the synthesis of a zinc-containing protein named ZAG (Zinc-α2-Glycoprotein) that was isolated for the very first time in 1961. Today, ZAG is classified as a new adipocytokine that is released by fat tissue. ZAG’s influence on the lipid metabolism has not yet been fully mapped out, yet most studies suggest that ZAG is important for converting stored fat in the white fat tissue into energy in connection with fasting or hard physical training.
ZAG also affects the turnover of blood sugar (glucose) and low ZAG levels increase the risk of insulin resistance where cells’ ability to absorb glucose is impaired. Animal studies have revealed that intravenous ZAG therapy can improve the glucose uptake without affecting insulin levels 30 minutes after ingesting glucose. In the subcutaneous tissues, increased levels of ZAG play a role in the body’s insulin sensitivity and fat tissue. In overweight individuals, however, ZAG levels are related to the amount of fat tissue. In other words, lower ZAG levels mean more body fat.
White fat tissue, BMI, ZAG, and inflammation
Today, white fat tissue is looked upon as a highly important endocrine organ. Besides serving as a storage facility for triglycerides that are the body’s energy reserves, fat cells also produce a number of adipocytokines with anti-inflammatory and pro-inflammatory properties.
It is believed that slender people primarily produce anti-inflammatory cytokines such as ZAG and interleukin-4 in their fatty tissue. In contrast, the fatty tissue in overweight people is believed to primarily produce pro-inflammatory cytokines such as TNF-α and interleukin-6. Overweight people therefore produce more pro-inflammatory cytokines in their fat tissue, which contributes to the free radical burden and oxidative stress that are linked to lifestyle diseases. People who are overweight often suffer from chronic inflammation which lowers the release of ZAG from fat tissue even more. That way, the endogenous production of ZAG is proportionally and inversely related to fat mass and BMI.
ZAG as a biomarker and therapeutic zinc supplementation
The insufficient endogenous ZAG production becomes a vicious cycle where it becomes increasingly difficult to burn fat and carbohydrate and where it becomes more and more challenging to lose weight and control oxidative stress.
The authors therefore suggest using zinc and ZAG as biomarkers of different biochemical processes in the body. They also mention that zinc supplementation has therapeutic potential in the prevention and treatment of overweight. Their study is published in Nutrients.
Widespread zinc deficiency and effective supplements
Zinc deficiency is mainly a result of unhealthy eating habits and lack of protein. Other factors that weigh in are a large iron and calcium intake and overconsumption of alcohol. As mentioned earlier, overweight may also increase the need for zinc. The same goes for diabetes, ageing processes, celiac disease, and several types of medicine plus birth control pills.
The daily reference intake (RI) for zinc is 10 mg (in Denmark). According to the European Food Safety Authority (EFSA), the upper safe intake level for adults is 25 mg per day.
Many zinc supplements contain inorganic zinc sources such as zinc sulfate and zinc oxide that are difficult for the body to absorb. When looking for supplements, make sure to read the label. The body can easily absorb and utilize organic sources such as zinc gluconate and zinc acetate.
Michalina Banaszak et al. Zinc and the Innovative Zinc-α2-Glycoprotein Adipokine Play an Important Role in Lipid Metabolism: A Critical Review. Nutrients 2021
University of St Andrews. Zinc could be key to new diabetes treatments. MedicalXpress. March 1, 2021
Pernille Lund: Sådan får du styr på dit blodsukker og din vægt. Forlaget Ny Videnskab 2013
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